In order to obtain a higher spectrum efficiency promotion, the density of cell deployment is getting higher, the user interference in the same cell and inter-cell co-channel interference increasingly become the major factors limiting the network capacity, as shown in FIG. 1 and FIG. 2.
In the current research, it is mainly based on the interference avoidance and coordination technology of the network side, and the basic idea is to implement the interference avoidance at the sending side by means of precoding and coordinated scheduling of the network side. However, the interference coordination based on the sending party depends on the accuracy of Channel State Information in feedback to a great extent. According to the related research data, it indicates that the interference also can be well compressed by using an advanced receiving method, while compared to the interference coordination of the sending party, the pressure of channel information feedback can be relieved based on an enhancement of the terminal. Therefore, how to better compress the interference by optimizing the terminal receiving is an important direction to improve the spectrum efficiency effectively.
In an LTE system, a Common Reference Signal (CRS) is used to perform pilot measurement and demodulation, that is, all users use the CRS to perform channel estimation. When a precoding processing mode based on the CRS is adopted, a transmitting end is required to additionally inform a receiving end of specific precoding matrix (also can be called as precoding weight) information used during the data transmission, and the pilot overhead is large. Moreover, in Multi-user Multi-input Multi-output (MU-MIMO), since a plurality of terminals use the same CRS, the pilot orthogonality cannot be implemented, thus the interference cannot be estimated.
In an Advanced Long Term Evolution (LTE-A) system, in order to reduce the pilot overhead and improve the accuracy of channel estimation, the pilot measurement function and data demodulation function are separated, and two types of reference signals are respectively defined: a Demodulation Reference Signal (DMRS) and a Channel State Information Referenced Signal (CSI-RS). Wherein, the CSI-RS is mainly used for channel measurement to obtain Channel Quality Information (CQI) and perform feedback, so that a base station side can complete user scheduling and complete adaptive allocation of the Modulation and Coding Scheme (MCS) through the information, and precoding information is not carried in the CSI-RS transmission; and the DMRS is mainly used for channel estimation of a Physical Downlink Shared Channel (PDSCH) and enhanced Physical Downlink Control Channel (ePDCCH) to complete demodulation of the data/control channels, and precoding information of corresponding PDSCH/ePDCCH is carried in the DMRS transmission. However, only the channel estimation performance of the target user is improved by these, and the interference measurement effect is not improved. And both the CQI measurement performance and the demodulation performance of the data/control channels are not only related to the channel estimation performance, but the interference measurement performance is also crucial.
In the LTE-A Rel-11 stage, even though a Channel State Information Interference Measurement (CSI-IM) signal is specially introduced in order to improve the CQI measurement performance, since the signal is not sent in each subframe, the actual interference of data transmission timeslots (subframes) cannot be reflected well, and interference information of each layer cannot be measured, thus it cannot be well used for Interference Cancellation/Interference Suppression (IC/IS) of the receiving side well in demodulation of the data/control channels. Therefore, how to improve the interference measurement effect and thus the demodulation performance of the data/control channels needs to be further studied.